To understand how any of the functional feature gaps that are present in Lightning Experience would affect you and your organization, you should consider carrying out work to assess the impact of a transition from Classic to Lightning Experience.
Given the significant differences in the user interface and the re-positioning of some features compared to Classic, training may be needed for users who are switching to the Lightning Experience theme.
As part of the assessment, you might want to consider carrying out a gap analysis for your Salesforce instance to generate a high-level impact assessment that you can create migration and adoption plans with. To assist with an assessment of the technical elements and possible impacts, various resources are available, all of which will be described in the following section.
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